Retrievable drilling apparatus for well bores



Aug. 21, 1962 A. w. KAMMERER, JR 3,050,142

RETRIEVABLE DRILLING APPARATUS FOR WELL BORES 2 Sheets-Sheet 1 Filed July 6, 1959 I I l l |I INVENTOR.

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Aug. 21, 1962 A. w. KAMMERER, JR 3,050,142

RETRIEVABLE DRILLING APPARATUS FOR WELL BORES 87 IN V EN TOR.

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7.70 NEY.

United States Patent O 3,050,142 RETRIEVABLE DRILLING APPARATUS FOR WELL BORES Archer W. Kammerer, Jr., Fullerton, Calif., assigner, by mesne assignments, of one-fifth to said Kammerer, one-lilith to .lean K. Lamphere, and three-fifths to Archer W. Kammerer, all of Fullerton, @alii Filed July 6, 1959, Ser. No. 825,126 21 Claims. (Cl. 175-260) The present invention relates to the rotary drilling of well bores.

Oil, gas, water, sulphur and similar well bores have her-tofore been drilled by securing a bit to the lower end of the string of drill pipe and lowering such pipe in the hole to its bottom portion, the drill bit then being rotated to continue the formation of the well bore. As each bit becomes dull, the drill pipe is removed from the well bore and another bit attached to it and the string of drill pipe relowered in the well bore. Alfter the desired depth of the hole has been produced, the drill pipe is removed and a string of casing or the like is lowered in the hole, which may be cemented in place.

The necessity for frequent round trips to change drill bits is a time consuming and costly operation. Potential damage to the well bore is also present due to pressures and the like developed in the drilling mud as a result of raising and lowering the string of drill pipe. There is also the danger of being unable to lower the casing in the drilled hole to the required depth, or in damaging the well formation during the lowering of the casing.

An object of the present invention is to provide comparatively simple drilling apparatus that avoids the necessity for repeated round trips of the drilling string to change drill bits, the apparatus being capable of being lowered and removed through a string of pipe which will form the ultimate casing for the well bore, and of being readily coupled to the lower portion of the pipe, which is then rotated to effect drilling of the hole, and of being released from the pipe and retrieved through its bore after the apparatus becomes dull or is to be retrieved for any other reason.

Another object of the invention is to provide a retrievable drill bit adapted to be lowered through a string of pipe to its lower portion and of being rotationally coupled thereto, the drilling bit having cutters expandible outwardly beyond the outside diameter of the pipe, and being compact and of strong and sturdy construction.

A further object of the invention is to provide a retrievable drilling bit having expandible cutters and capable of being lowered through a string of pipe to be rotationally coupled to its lower portion, there being no tendency for the cutters to expand during lowering of the bit through the pipe string.

An additional object of the invention is to provide a retrievable drilling bit having expandible cutters and which is capable of being lowered through a string of pipe to be rotationally coupled to its lower portion, the lower end of the pipe positively guiding the cutters into appropriate coupled relation to the pipe, wherein both drillling weight and torque are transmittable directly from the pipe to the cutters.

Yet another object of the invention is to provide a retrievable drilling bit having expansible cutters and adapted to be lowered through a string of pipe to be rotationally coupled to its lower portion, the cutters being expanded hydraulically by drilling fluid and being locked in their expanded position in such manner that the entire bit is, in effect, secured to the pipe against upward and downward movement with respect thereto.

n Still a further object of the invention is to provide a retrievable drilling bit having expansible cutters and 3,050,142 Patented Aug. 2l, 1962 ice adapted to be lowered and elevated through a string of pipe, and of being rotationally coupled to its lower portion, the cutters being locked in their expanded position and readily released from their expanded and locked condition to eifect their retraction, and thereby allow the entire bit to be withdrawn through the pipe to the top of the well bore.

This invention possesses -many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be be described in detail, for the purpose of illustrating the rgeneral principles of the invention; but it is to be understood that such detailed `description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

FIGURE l is a longitudinal section, parts being shown in side elevation of a drilling bit within and at the lower portion of a string of casing, or similar pipe, the apparatus being in its initial retracted position;

' FIG. 2 is a View similar to FIG. l, illustrating the drilling bit with its cutters in their expanded condition coupled to the string of pipe;

' FIG. 3 is a longitudinal section, on an enlarged scale, of the upper portion of the apparatus, showing the latch device in the position it occupies with the bit in the FIG. 2 condition;

FIG. 4 is a cross-section taken along the line 4-4 of FIG. 3;

FIG. 5 is a cross-section taken along the line 5-5 on FIG. v3;

FIG. 6 is a section taken along the line `6-6 on FIG. l;

FIG. 7 is a fragmentary side elevational view of one of the cutter devices in expanded position and coupled to the lower portion of the string of drill pipe or casing.

The apparatus illustrated in the drawings includes a lower portion 1t) of a string of well casing A, or similar pipe, which extends to the top of the well bore B being drilled. This string of pipe is rotated to transmit the drilling torque and drilling weight to `a retrievable drilling bit C adapted to be coupled to the lower or shoe portion 10 of the pipe string. The drill bit is movable down through the string of casing A, that is already disposed in the portion of the well bore B previously drilled, and iS releasably coupled to the shoe portion of the casing, after which the drilling of the well bore can proceed by rotating the string of pipe or casing and moving it progressively downwardly as the hole is produced, to move the cutters 11 of the bit against the formation. During the rotary drilling operation, drilling mud, or the like, is pumped down through the interior of the casing string A and discharges from the bit C to carry the cutting upwardly and around the string of the casing to the top of the hole. When a bit becomes dull, it is uncoupled from the casing string and withdrawn through its interior to the top of the hole, whereupon the same drill bit with new cutters or another drill bit is lowered through the casing string and clutched tor coupled in place to its shoe 1l). When the new cutters become dull, the drill bit is again withdrawn through the interior of the casing string and the cutters replaced. The foregoing action is repeated as often as necessary to drill the hole B to the desired depth. It is to be noted that the casing string need never be withdrawn from the well bore during drilling of the hole. lIt is only necessary to add additional sections at the top of the well bore as drilling proceeds. In fact, `after the hole has been drilled to the desired depth, the casing string can remain therein to be cemented in place, if desired, in substantially the same manner as casing strings are ordinarily cemented in well bores.

-piston which may be closed The drilling apparatus C specically disclosed in the drawings includes an elongate body 12 having a lower threaded box 13 to which a pilot bit 14 can be secured, as by threading its upper pin end 15 within the box. Above its threaded box the body of the bit has a transverse slot area 16 in which a plurality, such as a pair, of cutter devices are mounted. As specifically shown, cutter supporting members 17 are disposed in the elongate body slot 16, being pivoted on hinge pins 18 extending across the slot and suitably secured to the body 12. Each cutter supporting member 17 carries a cutter member 11, such as a conical toothed cutter, which, when expanded outwardly in the manner described hereinbelow, will drill the hole B to a diameter substantially greater than the outside diameter of the string of well casing A and enlarge the diameter of the pilot hole D drilled by the pilot bit 14.

The cutters 11 normally occupy an inward position, such as disclosed in FIG. l, in which they are retracted substantially fully within the confines of the body 12 of the tool. They are expanded outwardly of the body to be coupled to the drill pipe A as a result of downward movement of a mandrel device 19 within 'the body 12. As

shown, the mandrel device includes lan upper piston portion 20 slidable within a cylinder 21 in the body, leakage of iiuid between the piston and cylinder being prevented by a suitable seal device 22, such as a rubber or rubberlike lO ring, in an internal groove 23 in the body slidably and sealingly engaging the periphery of the piston. Secured to the piston 20 and depending therefrom `is a tubular member portion 24 of the mandrel, the lower portion of which is slidable through a guide 25 extending Yacross the body slot 16 and attached to the body 12. The

upper portion 26 of the tubular member 24 is piloted within the piston 20, its upper end engaging a downwardly facing piston shoulder 2 Downward movement of the tubular member 24 with respect to the piston 20 is prevented by a row of balls 28 which engage a downwardly facing raceway 29 on the tubular member and which -are received within an internal raceway 30 in the piston. The balls 28 are insertable through a radial hole 31 in the by threading a suitable plug 32 in such hole, as disclosed in FIGS. 1 and 2. Leakage of iluid between the piston and tubular member is prevented by a side seal ring 33.

When the piston 20 and tubular member 24 move downwardly, an expander 34 mounted on the tubular member .engages downwardly Iand inwardly tapering expander surlfaces 35 on the cutter Isupporter mem-bers 17 to -pivot the latter and the lcutters 11 above the axes of the hinge pins 18 and shift the cutters 11 outwardly. When the cutters have been shifted outwardly to their maximum extent, holding surfaces 36 on the expander 34 will be disposed behind companion holding surfaces 37 on the supporting members below their respective expander surfaces 35, preventing inadvertent retraction of the cutter supporting members 17 and cutters 11 :from their expanded position. rThe piston and tubular member portions 20, 24 of the mandrel are shiftable downwardly to the maximum extent determined by engagement of the lower end of the expander 34 with the guide 25.

As specifically disclosed in the drawings, the mandrel 19 is normally urged in an upward direction and held in such position, in which the expander 34 is disposed above the expander surfaces 35 on the cutter supporting members I17, by a helical compression spring 38 disposed in the cylinder 21 below the piston 20, the upper end of the sp`ring engaging the lower end of 'the piston, and the lower end engaging a lower spring Vseat 39 formed in the .body 12 -of the drill lbit. The mandrel member 19 is shifftable downwardly to expand the cutters 11 in response to iiuid pressure developed in the body 12 of the tool above the piston 20, which `is obtained by pumping drilling mud, or similar iluid, down through the casing string A. Such tiuid will flow through the upper end of the body I2 and then through inlet ports 40 in the mandrel y19 above its piston portion 2t) into a central passage 41 extending through the tubular member 24. Such 'liuid under pressure ilows through a nozzle 42 'at the lowerV end of the tubular member and discharges into the body slot 16. Because of the throttling action provided by the inlet ports 40 or by the nozzle 42, a back pressure is built up in the body 12 above the piston 20 which will urge the latter downwardly against the force of the spring 38 and urge the mandrel 19 and its tubular member 24 downwardly to etfect outward expansion of the cutter supporting members 17 and the cutters 11 carried thereby.

Once the cutters 11 have been expanded outwardly they are releasably locked in such outwardly expanded position. To accomplish Vthis purpose a carrier member 43 forms an upward extension of the mandrel 19. The lower end 44 of this carrier member is piloted into the upper head portion 45 of the mandrel being suitably secured thereto, as through use of welding material 46. This carrier extends upwardly through a spider or latch sleeve 47 mounted in the upper end of the body 12, having inwardly directed ribs 48 circumterentially spaced from one another and which are engageable with the periphery of the carrier. The latch sleeve 47 is held within the body by a split, snap retainer ring 49 overlying the upper end of the sleeve and disposed within an internal groove 50 in the body, downward movement of the latch sleeve 47' in the body being prevented by engagement of a sleeve iiange 51 with an upwardly directed body shoulder 52.

The carrier member 43 has an elongate slot 53 extending therethrough receiving a latch member 54 pivotally mounted on a hinge pin 55 extending across the carrier slot and suitably secured thereto, as by welding. The latch 54 also extends within a slot 56 in a retrieving plunger 57 movable longitudinally in a bore 58 in the latch carrier 43, downward movement of the plunger within the carrier being limited by engagement of a plunger flange 59 with the upper end of the carrier. The latch 54 is swingable outwardly of the carrier 43 under the influence of a helical compression spring 60, one end of which engages the inner wall of the ycarrier 43 and the other end of which engages an upwardly extending lug or spring seat 61 on the latch to force a latch linger 62 outwardly of the of the spider 47.

aligned with one of the ribs 48 by attac 'ng screws 63 to the carrier -43 on opposite sides of another rib 48, thereby maintaining the orientation of the latch 54 relative to a spider rib.

Initially, the mandrel 19 and the thereto are disposed in body 12 (FIG. l). disposed inwardly of surface of one of the carrier 43 attached an upward position within the bit At this time, the latch finger 62' is the carrier 43 and engages the inner spider ribs 48. However, when the mandrel 19 is moved downwardly by the pressure of the iuid pumped down through the casing string A, the carrier 43 and latch 54 move downwardly with it until the latch finger is disposed below the rib 48, the spring 60 then swinging the latch 54 outwardly until its linger 62 is under the rib (FIG. 3). The return or retracting spring 38 engaging the underside of the mandrel piston 20 is then incapable of elevating the mandrel 19 within the body 12 of the drill bit.

When the latch 54 is in its latching position, such as shown in FIG. 3, the hinge pin 55 in the 'latch is relieved of the latching force. The hole 5S in the latch is made elongate, permitting a slight longitudinal shifting of the latch 54 within the carrier slot 53 and across the pin. Thus, when the upper end of the latch linger 62 engages the lower end of a rib 4S, the lower end 65 of the latch will engage the lower side 67 of the carrier defining the carrier slot 53'. It is evident from FIG. 3 that the hinge pin 55 is relieved of the thrust transmitted through the latch 54 between the carrier `43 and the spider 47.

The flatch 54 is released, whenever the cutters 11 are to be retracted, by moving the retracting plunger 57 upwardly. This plunger has a retrieving pin 68 secured thereto which is slidable in diametrically opposed longitudinal slots 69 in the carrier and which pass through an opening 70 in the latch. Initially, the retracting pin 68 is in the lower position within the carrier slots 69- and the latch opening 70. When in this position, the latch `62 is free to swing outwardly under the influence of its spring 60' upon lowering of the mandretl 19 within the body 12. At this time, it is to be noted that the left side 71 of the latch opening 70", as seen in FIG. 3, is 1nclined in an upward and outward direction. Accordingly, when the retracting plunger 57 is elevated within the carrier 43, the retracting pin 68 engages the inclined side 71 of the latch 54 and swings it inwardly against the force of its spring 60, and completely within the confines of the carrier 43, thereby releasing the latch finger 62 from the spider rib 4S and allowing the entire mandrel 19 to move upwardly within the body 12 of the tool. In the event that the retracting spring 38 is used, it may exert sufficient force to elevate the mandrel 19 within the body 12, thereby allowing the cutters to return to their retracted position. However, if a retracting spring 3S is not used, then the elevation of the retracting plunger 57 to release the latch 54 will bring its pin 68 in contact with the carrier 43- at the upper end of the longitudinal slots 69, whereupon the upward force on the retracting plunger 57 will be transmitted through the -retracting pin 68 to the carrier 43, which is actually a part of the mandrel 19, the mandrel then being forcibly moved upwardly within the body 12 of the tool. If the elevation of the expander 34 above the expander surfaces 35 on the cutter supporting members 17 does not result in the cutter supporting members 17 and cutters 11 moving inwardly under the force of gravity to the retracted position Within the body 12, the upward movement of the mandrel will cause a retracting ange or shoulder 75 on the mandrel to engage the upper inner arms 76 on the cutter supporting members 17 and shift such arms upwardly and pivot the portions of the cutter supporting members 17 below the hinge pins 18, and the cutters 11 themselves, inwardly back within the confines of the body slot 16.

The retrievable drill bit apparatus C is adapted to move downwardly through the entire string of casing A to the shoe portion of the latter. It can move downwardly to the extent limited by engagement of a stop ring or thrust collar 77 on the upper portion of the body 12 with a stop shoulder 78 provided in the casing shoe. When the stop ring 77 engages the casing shoulder 7S, the pilot Ibit 14 is disposed substantially below the lower end of the casing shoe 10; whereas the lower portion 17a of each cutter supporting member 17 is disposed within a slotted coupling portion '79 at the lower end of the shoe, each cutter 11 being located below the lower end 8) of the shoe. The cutter supporting members 17 are expandible outwardly to be shifted within slots S1 in the lower portion of the shoe. The slots are sufficiently wide to accommodate a cutter supporting member 17 and each slot has a driving face S2 adapted to engage the side of a cutter supporting member in order to rotate the latter. The upper end 83 of each slot is defined by a thrust shoulder or surface adapted to engage a companion shoulder or step 84 on the cutter supporting member 17. The cutter supporting members 17 are shiftable outwardly of the body of the tool to the extent limited by engagement of an exterior surface 85 on each cutter supporting member above its stop shoulder 84 with the inner surface S6 of the casing shoe. Thus, the inner surface 86 of the casing shoe limits the extent of outward expansion of each cutter supporting member 17; whereas the holding surface 36 on the expander 34 coacts with the companion holding surfaces 37 on the cutter supporting members 17 to prevent inward movement of the latter.

The driving face 82 on the shoe, which will engage a companion face $7 on a cutter supporting member 17, is preferably flat so that a `substantial surface engagement is had between the driving face and the side face of the cutter supporting member. The opposed side 88 of each slot S1 is curved, the curve running from the inner surface 86 of the casing shoe 10, and thence toward its outer surface in a direction toward the driving face 82 of the slot, such as shown most clearly in `FIG. 6. The curved guide surface S8 will be engaged by the outer surface S9 or corner 90 of a cutter supporting member 17 when it is being expanded outwardly by the mandrel 19 shifting downwardly within the body 12, in the event that the cutter supporting members 17 are not aligned with a pair of diametrically opposed slots 81. The outward force will cause the cutter supporting members 17 to slide along the curved guide surfaces 88 in shifting to their outward position, until they move fully within the slots 81. Such arcuate shifting of the cutter supporting members 17 is accompanied by arcuate shifting of the body 10 of the tool. To facilitate such arcuate shifting, a rollable type of a bearing connection 911 is provided between the stop ring or thrust collar 77 and the body 12 of the tool. As shown, a set of balls 91 is mounted in an external raceway 92 in the upper portion of the body 12, and these balls engage a companion upwardly facing raceway 93 on the thrust ring 77. The balls 91 can be inserted between the raceways through a radial hole 94 in the body 12 of the tool, which is then closed by a suitable plug 95.

In the event that the cutter -supporting members 17 and cutters 11 are being expanded outwardly and the members 17 are disaligned with the slots 31, they might engage the curved corner 98 between a driving face 82 in one slot and the curved guide surface 88 of an adjoining slot. Because of the curved exterior 89 of each cutter supporting member 17, if it does not slide in a clockwise direction, as seen in FIG. 6, along the curved guide surface 88, it will slide along the corner 18a in a counter-clockwise direction into alignment with one of the slots 81, whereupon the cutter supporting member 17 is expandible fully outwardly to bring its stop surface 85 in engagement with the internal surface S6 of the shoe 10, and with its shoulder 84 under and adjacent to the downwardly directed thrust surface or shoulder S3 on the shoe. When the cutters 11 are locked in their expanded position by .the latch S4, the cutters cannot move upwardly of the shoe 10, which is also true of the body 12 of the tool; while the body of the tool itself cannot rno-ve downwardly of the shoe 10* by virtue of the engagement of the thrust collar 77 with the stop shoulder 78 on the body.

The pilot bit 14 will drill a pilot hole D Which is slightly less in `diameter than the minimum diameter through the casing shoe 10; whereas the expansible cutters 11, when expanded outwardly, will form 4and operate upon a transverse shoulder E in the formation that extends from the wall of the pilot hole D to the desired enlarged diameter of the Well bore B, which is substantially greater than the outside diameter of the casing string A. Drilling rnud can now be pumped down through the casing string and is prevented from passing around the exterior of the body 12 because of the provision of suitable side seal rings 98, such as rubber O rings, disposed in peripheral grooves 99 in the body and sealingly engaging the inner surface 86 of the casing shoe 'below its Stop shoulder 7 8. The fluid will then flow through the passages 100 'between the spider ribs 48 and the carrier 43, passing into the body 12 and downwardly around the carrier, continuing on through the inlet ports 40 and through the tubular member passage 41 to discharge from the nozzle 42. Such iiuid will discharge at a substantial velocity and `a substantial portion of it will flow into a fluid `guide 101 in the body of the tool at the lower end of the slot 16, which is suitably 'the thrust shoulders 83 on the shoe.

7 welded to the body. The fluid will pass through a fluid passage 14%2 in the lower portion of the body 12 and into 'a drill bit passage 103, discharging through the drill bit nozzles 164 to remove the cuttings from the drilling region of the pilot bit 14 and llushing them upwardly around the exterior of the bit and the casing back to the top of the hole. Some of the drilling uid discharging from the mandrel nozzle d2, as well as the drilling fluid discharging from the pilot bit nozzles 104, will also pass around the expansible cutters 11 and the transverse shoulder E on which such cutters are operating, carrying the cuttings produced by the expansible cutters upwardly around the exterior of the casing shoe 10 and the casing string A back to the top of the well bore B.

In the use of the apparatus, the cutters 11 are initially in the retracted Iposition disclosed in FIG. 1, and the latch S4 is also in its retracted position engaging the inner surface of the rib 48 with which it is oriented. The drill bit C is dropped into the string of Vdrill pipe or casing A and will gravitate through the -drilling mud therewithin until the thrust ring 77 engages the stop shoulder 78. Fluid can then be pumped down through the string of casing, passing into the body 12 of the tool and exerting a pressure on the piston portion to shift it downwardly and cause the mandrel expander 34 to engage the expander surfaces 35 of the cutter supporting members 17 to expand the cutters 11 outwardly. The cutter supporting members 17 will shift outwardly, and if disaligned with a pair of opposed shoe slots 81 they will engage either the curved guide surfaces 88 or the corners 98 of the shoe, to be shifted in one direction or another into alignment with the opposed slots 81, whereupon they will move outwardly within the slots to the extent determined by engagement of the upper exterior surfaces 8S of the supporting members 17 with the inner surface 86 of the shoe 10, at which time the thrust shoulders 84 on the cutter supporting members lare disposed under and closely adjacent to, if not against, The expander 34 maximum extent, disposed behind will also have moved downwardly to its in which its holding surfaces 36 are the companion surfaces 37 on the inner portions of the cutter supporting members 17. When this occurs, the latch 54 will have been shifted outwardly by the spring 60 to dispose its iinger 62 under a spider rib 48, thereby locking the mandrel 19 in a downward position within the tool body 12 and assuring that the cutter supporting members 17 'and cutters 11 will ybe held in their outward position.

The casing string A is then rotated at the proper speed `and the desired drilling weight then imposed down through the casing string onto the shoulders S4 of the cutter supporting members 17, such drilling weight being transmitted from the supporting members through the cutters 11 to the formation shoulder E. At the same time, drilling weight is being transmitted to the drill bit 14 to insure the production of the pilot hole D. Drilling mud is pumped down through the casing string while it is being rotated, the drilling mud discharging through the nozzle 42 and some of it removing the cuttings from the region of the expansible cutters 11, and other uid passing down through the pilot 'bit i4 to remove the cuttings in the pilot hole D, the cuttings from the different regions of the well bore vbeing flushed Iupwardly yaround the exterior of the casing A to the top of the hole B.

Drilling can proceed until the cutters 11 have become worn, after which the `drill bit C is removed without removing the casing string A from the hole. lSuch action can occur by lowering a suitable overshot (not shown) on a sand line (not shown) through the casing string, the overshot coupling itself to the head 11) of the retrieving plunger S7 which can then be pulled upwardly. Such upward pulling will cause the retrieving pin 68 to release the latch 54 from the spider rib 48, after which the mandrel 19 will shift upwardly within the body l2 to elevate the expander 34 above the expander surfaces 35 of the cutter supporting members 19. The cutter supporting members 17 will now shift inwardly. If need be to insure such inward shifting, the casing string A may be elevated a slight distance to remove the expansible cutters l1 from contact with the transverse vformation shoulder E.. Upward movement of the sand line will now result in upward movement of the entire grillling bit lC through the casing A t-o the top of the Another drill bit C can then be lowered in the well casing A, or the worn cutter portions 11, 14 of the removed drill bit replaced with new cutter portions, whereupon -the particular drill bit is again relowered through the casing string until the thrust ring 77 engages the casing shoulder 78, the -drilling iluid lagain being circulated down through the string of casing to shift the mandrel downwardly, to again expand the cutter devices 17, 11 outwardly until they are securely locked t0 and within the casing shoe 19, in `a manner disclosed in FIG. 2, the latch 54 preventing inadvertent upward movement of the mandrel 19 within the body 12 of the tool.

Merely by the expedient of coupling and releasing drilling bits C from the well casing A, the entire well bore B can be drilled without the necessity for removing the casing string A from the well bore. After the hole B has been drilled to the desired depth, the last used drill bit need merely be removed through the casing string to the top of the hole, whereupon the casing string can, if desired, be cemented in the well hole.

iIn the event that the pumping or drilling lluid through the well casing A ceases, as will occur when an additional casing section is to be added rat the top of the Well bore, the cutters 11 remain coupled in their outwardly expanded position to the casing. Such coupling yaction is retained because of the retention of the latch S4 under the rib 4S of the spider. The latch is only released when the retracting plunger 57 is moved upwardly relative to the latch carrier 43, in the manner described above. By disposing this latch 54 fully under one of the ribs l458 it is protected from the erosive action of the drilling uid passing downwardly through the spider 47 and around the carrier 43.

It is to be noted that the internal diameter of the casing shoe 1t), that is engaged by the seal rings 9S on the body 12 is less than the internal diameter of the casing shoe above the shoulder 73. in the event that the body 12 does not release readily from the casing shoe 10 when -the bit C is to be retracted through the casting string, the cutting devices 11 can be shifted to their retracted position within the confines of the ebit body 12, whereupon downweight can be imposed on the entire casing string. The pilot I.bit 14 will engage the bottom of :the pi-lot hole D .and prevent downward movement of the tbody 12. However, the casing shoe 1d can shift downwardly along the body until the seal rings 9S .are disposed above `the stop shoulder 78 of the casing ring. Since such seal rings have a lesser diameter than the internal diameter of the casing shoe and .string above ,the stop shoulder 7S, the body t2 will be freed from the casing shoe :and can be withdrawn lreadily to the top of the hole.

The inventor claims:

1. In a retrievable drilling bit adapted to be lowered within and coupled to the lower portion of a string of pipe disposed in a well bore, the lower portion having a lesser inside diameter than the pipe thereabove; a body movable longitudinally through the pipe and having an outside diameter substantially less than the inside diameter of the pipe `and of the lower portion of the pipe to permit fluid in the pipe to lay-pass around the body `when Lthe body moves longitudinally through the pipe above its lower portion; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; means on said body adapted to engage a lower portion ofthe pipe to prevent further downward movement of said body in the pipe and to locate the bit in the pipe with said cutter means extending below the lower end of the pipe; means on said body adapted .to seal against the lower portion of the pipe when said locating means engages .the lower portion; means movable longitudinally of said body after further downward movement of said body in the pipe is prevented 'for expanding said cutter means laterally outwardly of the body to drill an eective hole diameter .greater than the outside diameter of the pipe; and means vfor coupling the bit to the pipe, whereby the pipe is adapted 4to rotate the bit.

2. In a retrievable drilling bit adapted to be lowered within and coupled to the lower portion of a string of pipe disposed in a well bore, the lower portion having a lesser inside diameter than the pipe thereabove; a body movable longitudinally through the pipe and having an outside diameter substantially less than the inside diameter of the pipe and of the lower portion of the pipe to permit fluid in the pipe to by-pass around the body when the body moves longitudinally through the pipe above its lower portion; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; means on said body adapted to engage a lower portion of the pipe to prevent further downward movement of said body in the pipe and to locate the bit in lthe pipe with said cutter means extending below the lower end of the pipe; means on said body adapted to seal against the lower portion of the pipe when said locating means engages the lower portion; means movable longitudinally of said body after further downward movement of said body in the pipe is prevented for expanding said cutter means laterally outwardly of the body to drill an elective hole diameter greater than the outside diameter of the pipe; and means `for coupling said cutter means directly to the pipe, whereby the pipe transmits its rotary motion and torque directly to said cutter means.

3. In combination: a string of drill pipe adapted to be lowered within a well bore and having spaced longitudinal slots extending through the wall of its lower portion; a drill bit body movable longitudinally through said pipe; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; said pipe having stop means therein in its lower portion; means on said body engageable with said stop means to prevent further downward movement of said body in the pipe and 4to locate said body inthe lower portion of said pipe with said cutter means extending below the lower end of the pipe and in position .for lateral movement into said pipe slots; and means movable longitudinally of said body after further downward movement of said body in the pipe is prevented for expanding -said cutter means laterally outwardly of the body and into said slots to couple rsaid cutter means directly to said pipe, whereby yrotation of said pipe causes said cutter means to drill an eiective hole diameter greater' than the outside diameter of the pipe.

4. In combination: a string or" drill pipe adapted to be lowered within a well bore and having space longitudinal slots extending through the wall of its lower portion; a drill bit body movable longitudinally through said pipe; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; said pipe having stop means therein in its lower portion; means on said body engageable with said stop means to prevent further downward movement of said body in the pipe and to locate said body in the lower portion of said pipe with said cutter means extending below the lower end of the pipe and in position for lateral movement into said pipe slots; and means movable longitudinally of said body after further downward movement of said body in the pipe is prevented tor expanding said cutter means laterally outwardly of the body and into said slots -to couple said cutter means directly to said pipe, whereby rotation of said pipe Causes said cutter means to drill an eiective hole diameter greater than the outside diameter of the pipe; said pipe having thrust means at the upper ends of said slots engaging companion thrust means on said cutter means to transmit -drilling weight from said pipe directly to `said cutter means.

5. ln a retrievable drilling bit adapted to be lowered within and coupled to the lower portion of a string of pipe disposed in a well bore, the lower portion having a lesser inside diameter than the pipe thereabove; movable longitudinally th-rough the pipe and having an outside diameter substantially less than :the inside diameter of the pipe and of the lower portion of the pipe to permit iluid in the pipe to by-pass around the body when the body moves longitudinally through the pipe above its lower portion; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; means on said body adapted to engage a lower portion of the pipe to prevent .further downward movement of said body in the pipe and to locate the bit in the pipe with said cutter means extending below the lower end of the pipe; means on said body adapted to seal against the lower portion of the pipe when said locating means engages the lower portion; a mandrel movable longitudinally on said :body in one direction and engageable with said cutter means after -further downward movement of said body in the pipe is prevented for expanding said cutter means laterally outwardly of lsaid body to drill an effective hole diameter greater than the outside diameter of the pipe; releasable latch means acting between said mandrel and body to prevent longitudinal movement of said mandrel in the opposite longitudinal direction; and means for coupling the bit to the pipe, whereby the pipe is adapted to rotate the bit.

6. ln a retrievable drilling bit adapted to be lowered within and coupled to the lower portion of a string of pipe disposed in a well bore, the lower portion having a lesser inside diameter than the fpipe thereabove; a body movable longitudinally through the pipe and having an outside diameter substantially less than the inside diameter of the pipe and of the lower portion of the pipe to permit uid in the pipe to :by-pass around the body when the body moves longitudinally through the pipe above i-ts lower portion; initially retracted cutter means mounted on said body `for expansion laterally outwardly of said body; means on said body adapted to engage a lower portion of the pipe to prevent further downward movemen-t of said body in the pipe and to locate the bit in the pipe with said cutter means extending below the lower end of the pipe; means on said body adapted to seal against the lower portion of the pipe when said locating means engages the lower portion; a mandrel movable longitudinally on said body in one direction and engageable with said cutter means after further downward movement of said body in the pipe is prevented (for expanding said cutter means laterally outwardly of said body to drill an `eective hole -diameter greater than the outside diameter of the pipe; releasable latch mean-s acting Ibetween said mandrel and body to prevent longitudinal movement of said mandrel in the opposite longitudinal direction; means `for coupling the bit to the pipe, whereby the pipe is adapted to rotate the bit; and means for releasing said latch means.

7. In a `retrievable drilling bit adapted to be lowered within and coupled to .the lower portion of a string of pipe disposed in a well bore, the lower portion having a lesser inside diameter than -the pipe thereabove; -a body movable longitudinally through the pipe and having'an outside diameter substantially less `than the inside diameter of the pipe and of the lower portion of the pipe to permit tiuid in the pipe to by-p-ass around the body when the body moves longitudinally through the pipe above its lower por-tion; initially retracted cutter means mounted on said body lfor expansion laterally outwardly of said body; means on said body adapted to engage a lower portion of the pipe to prevent further downward a body movement of said body in the pipe and to locate the bit in the pipe with said cutter means extending below the lower end of the pipe; means on said body adapted to seal against the lower portion of the pipe when said loeating means engages the lower portion; a mandrel movable longitudinally on said body in one direction and engageable with said cutter means after further downward movement of said body in the pipe is prevented for expanding said cutter means laterally outwardly of said body lto drill an etective hole diameter greater than the outs-ide diameter of the pipe; releasable latch means acting between said mandrel and body to prevent longitudinal movement of said mandrel in the opposite longitudinal direction; means for coupling the bit to the pipe, whereby the pipe is adapted .to rotate the bit; and means for releasing said latch means and moving said mandrel longitudinally in the opposite direction in said body to enable said cutter means to retract.

8. In combination: a string of drill pipe adapted to be lowered within a well bore and having spaced longitudinal slots extending through the wall of its lower portion; a drill bit body movable longitu-dinally through said pipe; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; said pipe having stop means therein in its lower portion; means on said body engageable with said stop means to prevent lfurther downward movement of said body in the pipe and to locate said body .in the lower portion of sai-d pipe with said cutter means extending below the lower end of the pipe and in position for lateral movement into said pipe slots; and means movable lonigudinally of said body after further downward movement of said body in the pipe Iis prevented for expanding said cutter means laterally outwardly of the body and into said slots to couple said cutter means directly to said pipe, whereby rotation of said pipe causes said cutter means to drill an effective hole diameter greater than the outside diameter of the pipe; the inner wall of rsaid pipe engaging said cutter means to limit outward expansion of said cutter means.

9. In combination: a string of drill pipe adapted to be lowered within a well bore and having spaced longitudinal slots extending through the wall of its lower portion; a drill -bit body movable longitudinally through said pipe; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; said -pipe having stop means -therein in its lower portion; means on said body engageable with said stop means to prevent further downward movement of said body in the pipe and to locate said 4body in the lower portion of said pipe with said cutter means extending below the lower end of the pipe and in position for lateral movement into said pipe slots; and means movable `longitudinally of said body after Afurther downward movement of said body in the pipe is prevented for expanding said cutter means laterally outwardly of the body and into said slots to couple said cutter means directly to said pipe, whereby rotation of said pipe causes said cutter means to drill an effective hole diameter greater than the outside diameter of the pipe; said pipe having thrust means at the upper ends of said slots engaging companion -thrust means on said cutter means to transmit drilling weight from said pipe directly to said cutter means; the inner wall of said pipe engaging said cutter means to limit outward expansion of said cutter means.

10. dn combination: a string of drill pipe adapted to be lowered within a well .bore and having spaced longitudinal slots in its lower portion; a drill Ibit body movable longitudinally through said pipe; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; said pipe having stop means therein in its lower portion; means on said body engageable with said stop means to locate said body in the lower portion of said pipe with sai-d cutter means extending below :the lower end of the pipe and in position for lateral movement into said pipe slots; and means for expanding said cutter means laterally outwardly of the body and into said slots to couple said cutter means directly to said pipe, whereby rotation of said pipe causes said cutter means to drill Ian effective hole diameter greater than the outside diameter of the pipe, one side of cach slot confronting a side of said cutter means being curved outwardly from the inner wall of the pipe toward the other cutter means driving side of such slot .to be engaged by said cutter means and turn said cutter means fully into said 4slot during outward expansion of said cutter means.

1l. In a retrievable drilling bit adapted to be lowered within and coupled to the lower portion of a string of pipe disposed in a well bore, the lower portion having a lesser inside diameter than the pipe thereabove: a body movable longitudinally through Ithe pipe and having an outside diameter substantially less than the inside diameter of the pipe and of Ithe lower portion of the pipe to permit fluid in the pipe to by-pass around the body when the body moves longitudinally through the pipe above its lower portion; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; means on said body adapted to engage a lower portion of the pipe to prevent further downward movement of said body in the pipe and to locate the bit in the pipe with said cutter means extending below the lower end of the pipe; means on said body adapted to seal against the lower portion of the pipe when said locating means engages the lower portion; a mandrel reJ sponsive to the pressure of duid pumped down the pipe to be moved downwardly in the body and engageable with said cutter means after further downward movement of said body in the pipe is prevented for expanding said cutter means laterally outwardly of said body to drill an elective hole diameter greater than the outside diameter of the pipe; and means for coupling the bit to the pipe, whereby .the pipe is adapted to rotate the bit.

12. In a retrievable drilling bit adapted to be lowered within and coupled to the lower portion of a string of pipe disposed in a well bore, the lower portion having a lesser inside diameter than :the pipe thereabove: a body movable longitudinally through the pipe and having an outside diameter substantially less than lthe inside diameter of the pipe and of the lower portion of the pipe to permit lluid in the pipe -to rby-pass around the body when the :body moves longitudinally through the pipe above its lower portion; initially retracted cutter means mounted on said body yfor expansion laterally outwardly of said body; means on said body adapted to engage a lower portion of the pipe to prevent further downward movement Vof said body in the pipe and to locate the bit in the pipe with :said cut-ter means extending below the lower end of lthe pipe; means on said body adapted to seal against the lower portion of the pipe when said locating means enga-ges the lower portion; a mandrel responsive to the pressure of iluid pumped down .the pipe to be moved downwardly in the body and engageable with said cutter means after further downward movement of said body in the pipe is prevented for expanding said cutter means laterally outwardly of said body to drill an eiective hole diameter greater than the outside diameter of the pipe; releasable latch means acting between said mandrel and body to prevent upward return movement of said man- `drel in -said body; and means for coupling the bit to the pipe, whereby lthe pipe is adapted to rotate the bit.

13. In a retrievable drilling bit adapted to be lowered within .and coupled to the lower portion of a string of pipe disposed in a well bore, the lower portion having a lesser inside diameter than the pipe thereabove: a body movable longitudinally through the pipe and having an outside diameter substantially less than the inside diameter of the pipe and of the lower portion of the pipe to permit Huid in the pipe to by-pass around the body when the body moves longitudinally throughy the pipe above its lower portion; initially retracted cutter means mounted on said body -for expansion laterally outwardly of said body; means on said body adapted to engage a lower portion of the pipe to prevent further downward movement of said body in the pipe and to locate the bit in the pipe with said cutter means extending below the lower end of the pipe; means on said body adapted to seal against the lower portion of the pipe when said locating means engages the lower portion; a mandrel responsive to the pressure of uid pumped down lthe pipe -to be moved downwardly in the body and engageable with said cutter means after lfurther downward movement of said body in the pipe is prevented for expanding said cutter means laterally outwardly of said body to drill an effective hole diameter greater than the outside diameter of the pipe; releasable latch means acting between said mandrel and body to prevent upward return movement of said mandrel in said body; means for coupling the bit to the pipe, whereby the pipe is adapted -to rotate the bit; and means lor releasing said latch means and moving said mandrel upwardly in said body to enable said cutter means to retract.

14. In combination: a string of drill pipe adapted to be lowered within a well bore and having spaced longitudinal slots extending through the wall of its lower portion; a drill bit body movable long-tiudinally lthrough said pipe; initially retracted cutter means mounted on said body for expansion laterally outwardly of said bo-dy; said pipe having stop means therein in its lower portion; means on said body engageable with said `stop means to prevent lfurther downward movement of said body in the pipe and to locate said body in the lower portion of said pipe with said cutter means extending below the lower end of .the pipe and in position for lateral movement into said pipe slots; a mandrel responsive to the pressure of uid pumped down lthe pipe to be moved downwardly in the body and engageable with said cutter means after further downward movement of said body in the pipe is prevented -for expanding said cutter means laterally outwardly of said body and into said slots to couple said cutter means directly to said pipe, whereby rotation of said pipe causes said cutter means to drill an eilective hole diameter greater than the outside diameter of the pipe.

15. In combination: a string of drill pipe adapted to be lowered within a well bore and having spaced longitudinal slots extending through the wall of its lower portion; a drill bit body movable longitudinally through said pipe; initially retracted cutter means mounted on said body for expansion laterally outwardly of said body; said pipe having stop means therein in its lower portion; means on said body engageable with said stop means to prevent further downward movement of said body in the pipe and to locate said body in the lower portion of said pipe with said cutter means extending below the lower end of the pipe and in position for lateral movement into said pipe slots; a mandrel responsive to the pressure of fluid pumped down the pipe to be moved downwardly in the body and engageable with said cutter means after further downward movement of said body in the pipe is prevented for expanding said cutter means laterally outwardly of said body and into said slots to couple said cutter means directly to said pipe, whereby rotation ot said pipe causes said cutter means to drill an effective hole diameter greater than ythe outside diameter of the pipe; releasable latch means acting between said mandrel and body to prevent upward movement of said mandrel in said body; and means for releasing said latch means and moving said mandrel upwardly in lsaid body to enable said cutter means -to retract.

16. In combination: a string of drill pipe adapted to be lowered within a well bore and having spaced longitudinal slots in its lower portion, each slot having opposed driving and trailing sides; a drill bit body movable longitudinally through said pipe; `initially retracted cutter i4 means mounted on said body lfor expansion laterally outwardly of said body; said pipe having stop means therein in its lower portion; means on said body engageable with said stop means to locate said body in the lower portion of said pipe with said cutter means extending below the lower end of the pipe and in position for lateral movement into said pipe slots; a mandrel responsive to the pressure of fluid pumped down the pipe to be moved downwardly in the body and engageable with said cutter means for expanding said cutter means laterally outwardly of said body and into -said slots to couple said cutter means directly to said pipe, whereby rotation of said pipe causes said cutter means to drill an effective hole diameter greater than the outside diameter of the pipe; releasable latch means acting between said mandrel and body to prevent upward movement of said mandrel in said body; and means for releasing said latch means and moving said mandrel upwardly in said body to enable said cutter means to retract; the trailing side of each slo-t confronting a side of said cutter means being curved outwardly from the inner wall of the pipe toward the driving side of such slot 4to be engaged by said cutter means and turn said cutter means ttully into said :slot during outward expansion of said cutter means.

17. In combination: a string of drill pipe adapted to be lowered within 4a well bore and having spaced longitudinal slots in its lower portion, each slot having opposed driving and trailing sides; ra drill bit body movable longitudinally through said pipe; initially retracted cutter means mounted on -said body for expansion laterally outwardly of said body; said pipe having stop means therein in its lower portion; rneans on said body engageable with said stop means to locate said body in the lower portion of said pipe with said cutter means extending below the lower end of the pipe and in position for lateral movement into said pipe slots; a mandrel responsive to the pressure of iluid pumped down the pipe to be moved downwardly in the body and engageable with said cutter means `for expanding said cutter means laterally outwardly of said body and into said slots to couple said cutter means directly to said pipe, whereby rotation of said pipe causes said cutter means to drill an effective hole diameter greater than the outside diameter `of the pipe; releasable latch means acting between said mandrel and body to prevent upward movement oi said mandrel in said body; and means for releasing said latch means and moving said mandrel upwardly in said body to enable said cutter means to retract; the trailing side of each slot confronting a side of said cutter means being curved outwardly from the inner wall of the pipe toward the driving Iside of such slot to be engaged by said cutter means and turn said cutter means -fully into said slot during outward expansion of said cutter means; said pipe having thrust means at the upper ends of said slots engaging companion thrust means on said cutter means .to transmit drilling weight from said pipe directly to -said cutter means.

18. A shoe adapted to constitute the lower portion of a string of pipe disposed in a lwell bore, comprising a tubular member having circumferentially spaced slots extending upwardly from its lower end, each slot being defined by opposed side walls; one side wall of each slot being curved outwardly from the inner wall of said tubular member in a direction toward the other side wall of said slot.

19. A shoe adapted to constitute the lower portion or a string of pipe disposed in a well bore, `comprising a tubular member having circumferentially spaced slots extending upwardly from its lower end, each slot being defined by opposed side walls; the side walls of each slot being substantially parallel to the axis of said tubular member; one side wall of each slot being curved outwardly from the inner wall of said tubular member in a direction tow-ard the other side wall of said slot.

20. A shoe adapted to constitute the lower portion of a string of pipe disposed in a well bore, comprising a tubular member having circumferentially spaced slot-s extending upwardly from its lower end, each slot being dened by opposed side walls; Athe side walls of each slot Ibeing substantially parallel to the axis of said tubular member; one side Wall of each slot being curved outwardly from the inner wall yof said :tubular mem-ber in a `direction toward the other side wall of said slot, the upper end of each slot being substantially normal to the axis o-I said tubular member.

21. A shoe adapted to constitute the lower portion of a string of pipe disposed in a well bore, comprising a ytubular member having eircumferentially spaced slots extending upwardly from its lower end, each slot being dened by opposed side lwalls; one side wall of each slot References Cited in the file of this patent UNITED STATES PATENTS 1,159,172 Buick Nov. 2, 1915 1,326,509 Humason Dec. 30, 1919 1,360,328 Stokes Nov. 30, 1920 1,395,081 Barry et al. Oct. 25, 1921 1,659,769 Dodds Feb. 21, 1928 1,783,580 Miller Dec. 2, 1930 2,277,989 Kinnear Mar. 31, 1942 2,287,714 Walker June 23, 1942 

